Surgical filaments are made from a wide variety of materials in order to satisfy the full range of surgical and medical needs. Illustrative materials from which surgical filaments are made are surgical gut, silk, cotton, steel, nylon, polyester, polypropylene, lactide homopolymers and copolymers, polydioxanone, and others. Despite the many different materials from which surgical filaments are now made, there is a continuing search for new materials in the hope of improving deficiencies of the currently available materials, or in the hope of providing combinations of properties not presently obtainable.
It has recently been proposed to produce surgical sutures from polyvinylidene fluoride. It was observed, for instance, that such sutures have very high tensile and knot strength. The inventors herein have found, however, that the compliance (as is evidenced by the Young's modulus) of monofilaments made from polyvinylidene fluoride homopolymer is a little high, thereby limiting the utility of monofilament sutures made from such materials. The inventors herein have also found that if one subjects vinylidene fluoride homopolymer monofilament to an annealing with relaxation or shrinkage step so as to reduce the Young's modulus, and thereby increase the compliance, the elongation of such monofilaments is increased to the point where the monofilament is very "stretchy", and therefore its usefulness is reduced.
This invention is based upon the discovery that certain vinylidene fluoride copolymers can be fabricated into surgical filaments that have an excellent combination of properties, including acceptable tensile and knot strength as well as excellent compliance.